Power tube



July 20 1948. l. w. cox ET AL POWER TUBE Filed Jan. 30, 1946 Patented July 20, 1948 21min 1W. 130x, West ,Allis,

mend, .illlilvv.znlkoe.v Wis.,

and Lester 1). Drugassignors to Cutler- ;Hammcr, Inc Milwaukee, Wis, a corporation of lllelaware Application January -30, 1946, Serial No. 644,270 zzl'filaiins. (o1. 250F215.)

This invention relates to improvements in power tubes, andathezinventionv-relates more par! ticularly to'a tubelembodying a pool type-cathode.

The purpose of this .invention;is .to provide -a reliable starter, of exceedingiy :long :life :(of more than onehundredtimesthe lifeofzthe lwellknown banclstype starter), for :a power atuhe of "the reconstructible cathode :type, which --tube will operate not only efor conduction of relatively large values 'Qf energy, hutlalsoior "conduction of relatively small values vof energy comparable :to the values required 1 to influence the iiisoharie :01 a hot cathode type of tubethavins eridcontrol, such as a Thyratrom AllacfiSQMlfllfifiMflifiQf the starter herein cont mplated is the provision of a substantially unidirectional-streamer ietl vapor of the sam m terial :as thatoi whi h the po l two oath .de ,isziormed, which, jet is ionized only atthe instant atwhichit-is; desired to start conduction in the'tube, Thetimingoi the ioniz ing pulse is;accomplisl'ledin means of anapprop ate phaseo ntrol oircuit,-andth 1jet is dir cted toward the reoonstru tible cathode (usually ,a mercury cathode) so that when the jet islim iZcd it starts an arc spotat the p int wherelit .imh nges upon the cathode surface amiat the instant of ionization. Thestartinghoi .th sljarc spot in accordance with 011 invention YfiIY rapid, and very reliable, audits fioroycle ,PIQdl10- tion, as an averagarequiresless than one watt of 60 cyclev ionizing ener y Thetfollowinglare some oft-the advantages oi such a starter:

1. The source or the ionized vap r reconstructible and hence indestructible:- Theiiouizingragent is a unidirectional ga vstream nd is unafiected by relatively large variations in the height or level oiithe cathode pool, inasmuch as the vapor o the jetfis traveling atthe enormous molecular velocity associated with its temperature.

2. The ionizing origniting agent is itself of the nature of anare at theinstantit'impinges upon the surface of the cathode, and wes'have'foundin practice that it will start an arc from the cathode to the anode within atime period of'the-or'der of a microsecond.

3. Inasmuch as theaveragewatta-ge necessary for the ionization at m oyoles is'less than one watt, deterioration of the starter elements :i'here tofore always associated oentration) cannot :take place, semi long Ellie star the starter (and -consequentlvzrorrthe tubeva za whole) thus. insulted.

4. Thelow-wwattage:necessaryziorzthe startin withihighrenergyneonlmeans decre ses the total amo t of ene y which 3,1151? be dissipated by the cooling means (when employed), so that a tube with limited cooling means may berated as much as twentyfive per cent higher, when usinga starterof the haracter herein dis l sed, as ompared with a similar tube employing the usual igniter rod. For example, a, 16 kilowatt tube (in a 440 vOr zt, 60 cycle alternating current circuit) vhaving a cooling system just sufficient when using an isniter rod, may be rated as a 20 kilowatt tube (with the same cooling system) when thestarter herein s d. is empl y and the same amount of heat will be carried away.

5. Qt verygreatimportanoe, is the fact that the demand energies are so much lower for the starter herein disclosed than for the conventional formof igniter rod starter that eventhe smallest f the-T yratron ype of tubes ar more than adeguateflior its control. The control unit for the tube herein disclosed may be compact and inexpensiva and make small demand in respect o power consumed,whileminimizing the moun of heat generated-in the control cabinet. The starter herein disclosed is so reliable thatprope operationofthetube isinsured even h gh the current passing therethrouehis varied ,i rn a value of hundreds of amperes down to, a value of aiewmilliamperes, by means of phase control, without any other change in the circuit, Eor example; a continuous decrease in ,current Irom a relatively high value to a value lowerthan 5 milliamperes may beefiected with a tubeof the character herein contemplated.

la -p imary object of the invention isto provid a novel form of starting means for slloh'tllbes which is .more rapid and hence more reliable than starting mcansherctofore proposed.

Another and more specific objectis to provide foruseof anionized vapor jet as the starting medium for the tube. 7

Another object is to provide for generation of the wapor oi the jet-from a-body ofmaterial like that of thelcathode but arranged in electrically insulated relationshipto the latte Another object is to provide an electrically insulated boileraforthe separate body of cathode material having associat d therewithan auxiliary electrode whereby the-generated vapor maybe substantiallyinstantaneously ionized at will.

,-Another object is :to provide for impingement oi :at-.-least a portion 1 of ,the ionized vapor of-the Set against @a di lectric lement at a p nt-closely ad acent tth po nt-of mp ng ment of :said jet againstuthe oathodesuriaoe.

Another object is to provide a source of ionized vapor which is reconstructible and hence indestructible.

Another object is to provide an ionizing agent traveling at a very high molecular velocity corresponding to its temperature, whereby the same is functionally efiective regardless of relatively large changes in the level of the cathode pool.

Another object is to provide an ionized igniting agent which is itself of the nature of an are at the instant it impinges upon the cathode sur-. face, whereby the time required to start an are from the cathode to the anode is minimized,

Another object is to minimize the wattage necessary for ionization of the igniting agent to correspondingly increase the effective life of the tube.

Another object is to utilize such minimized wattage to afford a substantially increased rating of the tube.

' Another object is to provide a tube of the aforementioned character wherein the starter is so reliable that the value of current transmitted by the tube may be varied from hundreds of amperes to a few milliamperes by means of phase control without any other change in the circuit. Other objects and advantages of the invention will hereinafter appear.

The accompanying drawings illustrate certain embodiments of the invention which will now be described; it being understood that the invention is susceptible of embodiment in other forms within the scope of the appended claims.

In the drawings:

Figure 1 is a vertical sectional view of a power tube having our improved starting means incorperated therein. I

Fig. 2 is a fragmentary side elevational view of certain elements of the tube shown in Fig. 1.

Fig. 3 is a sectional view, on the line 33 of Fig. 1. V

Fig. 4 is an enlarged fragmentary sectional view of an arrangement of parts similar to that shown'in Fig. 1, but illustrating a modification wherein portions adapted to substantially. simultaneously impinge against a dielectric element and the surface cf the cathode. Fig. 5 is a fragmentary elevational view of certain of the elements shown in Fig. 4; the normal level of the cathode pool being indicated by the dotted line. I

Fig. 6 is a fragmentaryvlew similar to Fig. 5, but showing a modified form of dielectric means against which the vapor jet is adapted to impinge, and v Fig. 7 is a fragm'entary'sectional view of a device similar to that shown in Figs. 1 to 3," but with the upper end of the hood or dome omitted and with the belief the boiler attached at a plurality of points to the overflow weir for support of the former.

Referring first'to Figs. 1 to 3. the numeral l designates an evacuated and sealed tube or flask, which is here shown as composed of glass of suitable composition. The main body of tube is preferably of substantially circular form in transverse cross section portion of its length. Tube I0 is provided at its upper end with a downwardly and inwardly convergent annular flange ll having the relatively thicker top portion l2 formed integrally therewith. Portion l2 isformed as shown at l3 to afiord a glass to metal seal with respect to intermediate portion Hi of an anode leadwhose of the ionized vapor jet are throughout the major upper and lower portions are'designated by numerals l4 and W. The section l4 is composed of a metal, such as tungsten, suitable for cooperation with the glass seal l3, and sections l4 and i may be composed of any other metal or metals suitable for their respective purposes, and united with portion M as by welding. Portion M is welded or otherwise rigidly connected mechanically and electrically to the anode l5, which may consist of a ring or tube section composed of iron. Although I have shown only one anode lead I i, l4, l4, it is to be understood that in practice two or three of such leads will ordinarily be employed. I

Numeral l6 designates the upper portion of a cathode lead; the same being united with one endof an intermediate portion l6 which is surrounded by a glass seal I 3. Attached to the lower end-of portion I6 is a relatively long portion I 6* whose lower end is immersed in the mercury: pool I! which forms the reconstructible cathode of the tube. In practice said portion [6 has its lower end bent at substantially a right angle thereto, as indicated at I6", to form a supporting shoulder for the lower end of a glass tube I8, whose .upper end surrounds and is fused or sealed to the hollow tubular extension 13 of the glass seal l3; Bythis means the portion [6 of the cathode lead is properly insulated from the anode 15, while providing for circuit connection .of both the anode and the cathode at the upper end of the tube. Ifdesired, one or more additionalcathode leads I'G, I64, Ni 16, each having a glass tube Idassociated therewith, may be employed in the power tube Hi.

The top portion member '19 rigidly attached toand communicatingwith the interior thereof to provide for exhausting, the interior of tube lflto the desired degree, as by means of a suitable vacuum pump (not shown); After creation of the desired degree' of yacuumwithin tube 10, member I9 is fusedat 'a given point to provide 'a seal or closure'lll I V The'portion Hi of tube I0 which supports the mercury pool I! is duced diameter, as shown.

Our novel starting means for tube It] is mounted at the lower end thereof in proper relationship to the cathode pool l1. Said means as shown comprises a glass hood or dome 28 whose lower edge 28* is fused to seal the same to the peripheral edge of an opening formed in the bottom wall Iii of tube It]. Hood 20 is provided in itsfperipheral'wa'llwith an opening 20", here shown; (Fig. 22' as of substantially rectangular contour; the lower edge of opening 20 acting as a weir to provide for. overflow of the mercury of pool H when the same rises above a predetermin'ed level. Openinglll also provides for outwardflow or projection of a jet ofmercury vaporintov contactewith the surface of cathode poolv li in the manner illustrated and hereinafter described. v I Hood .20 has fused thereto at 2| (for support thereby) a glass bell 2| having a relatively long downward tubular extension 2|", to the lower end of which an upwardly extending tubular glass member .2I 'is rigidlyunited, as by fusion, at the pointll Member 2lextends substantially throughout the length'of extension 2| and has its upper peripheral edge bent inwardly toward, but out of sealing contact with, said extension 21'; the member. 2| being. peripherally spaced I 2 of tube It! has a tubular preferably of substantially reoutwardly rrom extension 2 to prewar: a heat insulating spaced therebetween.

Fused to the lower surface 40 of t'ulo'e l m'in ali-nement and in eommunioation with hood 28, is 'a'gla'ss chamber member -2 2; the "latter *having a *reentrant tubular portion 22 romeo centrally thereof to extend upwardlythrmighoiit the length "of extension *2 and into the aforementio'ned bell 21; the olose'd upper end 'df portion 22 being designated by numeral 22.

The aforementioned member 21'' is preferably provided at vertically spaced points with sets of three or moreoutwardly'prdjeetihgdeesses (shown as of hollow forination, andfleslgnate'd by numerals Z-l and 2 l respectively) Said 'hosse's" 2 l andj fi' are accommodated Within, but are elos'ly adjacent tothe peripheral 'i nnersurface of chember 22 to stabilize andins'ure 'pes itiori-ih'g ofthe extension fl and member 24 within *ha'inber 2 2, BelI Zi has a relatively-small opening 2h formed therein and angled downwardlyjas'shown in Fig. 1 to provide for passage "of th'e 'va 'or jet orstr'eam therethroughand'throughthe opening for impingement thereof against the surfaee of cat ode l1.

Positioned. within the reefitra'ht tubular porhon-22* is an electric heating "-eieme'rit'off any suitable form. The heating elementis "shown as comprising acylind'rical core-or rod 23 formed of porcelain or similar ceramic "material, upon the exterior of which isc'oiled a flat strip 24 Of suitable resistance material; as, for-instance, "a strip composed of an alloy of'ni'ckel'ari'clfchrm miurjn, the'colls of the stripbeing 'substantially spaced from each other as illustrated. A'wire 1e'ad 25 is welded, brazed, or otherwise electrically connected. to the low'ef'end coil of strip 24, and a wire lead 26 is similarlyconneetedito the upper end coil; core 23 having a through passa'ge formed therein to "accommodate lead 26 a nd to insulate the same iromall but' said upperend (Soil.

Leads "25 and "2.6 are adapted to be connected in circuit :wi-th any "suitable source "of energy supply (not shown). 'In'praetiee'electri'c current issupplied to'the strip 24 "of resistancematerial a short tirne'before it is desired'tos'tart tubeifl in operation, and'th'e heater then'remai'nsln circuit throughout the operation oi -'the power tube.

Chamber 22 as shown-is adapted'to eontain a body of mercury H? which l5 normally-eloqtrieally and 1 mechanically insulated or sepa'rated from thec'athode l1. '-We prefer toprovid'wthe chamber 22 with an outward anrfxila'r bulge or r'ec'zess 22 to increase the snria'oe'area of the mercury body H at or adjacent the 'n'orrrialle'vl thereof Within chamber 22. Prior toeohiplti'on of the heater circuit it will 'he appa-rent that 'the mercury of body 11 will extend upwardly in a thinhririularor-tzibular shape -l -l 'hetween the outer surface or reentranttubu'lar portion 22 and the inner surface of the aforementioned downward extension 2P to approximately the same level as that portion 'of mereii'ry body F1 between Chamber 22 an'd the 'outer=-siirface of member 2!. Upon completion of theheater circuit the portion I 1 ofinercury'body H 'will be rapidly heated to a temperaturesiioh as tocause generation of mercury 'vapor, which is released at'the' upper surface-thereof and-flows upwardly into i thehell '2 I as" indicated at 5 H "sueh vapor being" further heated 'diuiri iiig' its Ward new.

The Vapor-is perni'ittd to *escape throu'gh i the openin 2 l arcsrmemion" d, and upon develop-- ment -ef sufilclent prssure 'the vapor mu 1 across theopenl-nglfl efdoted' in the form'et a Jet i l whlh'is to impinge against the surrece or the rner ouri'y pool M at a. :poirit adjacent the :o'pening 20 thYough-Wfiifih theijet passes.

We have foflnd thait by ionizing the mercury vapor, ot which the jet is composed, it is "possible to start on are :irom the cathode F1 to the :anode almost instantaneously. E-Hat is to sa y, in a time perm- 1 of Who order or e inicr'osecond. For this purpose we prefer "to provide an ugmter read, *or aumiary electrode 21 having an inte'rmedlate portion 11* of o, mas-a such as tungsten which is surrounded hy a g'las's seal M mi-med m' the pei lpheral wall or chamber 22, and an inner "end portion 11 which oontacts with the *body of mercury t! =a substantial :distan'e'e below the upper surfiace of the latter.

hny suitable' eiro'uit arrangement (not shown) may be provided for energizing the auxiliary electrode 21 either -=simu1tane'ous1y "or *subsequently "to enei glzatlon 'of the anode W5 and cathode W; suh nieans, of course, bein g ar sni'tablemariner 'to insure that the eleetrioa respe'et t'o' the pofiential of cathode I"! "to'irisure starting 0f tube 10. As atoreindicated --both the cathode pool 1-! and the m'ercury b'o'cly l 'l *are automatically 'reconstrueted during operation of tube 10. i

We 'have found by experiment that the ionized vapor Jet starting-means herein fllslosed mayia'e improved and made moan-enable, in respeet of insuring substantially inetantaneous starting of the power' t'ub'e by causing a portion, at least, of the *vapor ofthe "jet to contact -'or impinge upone boflYd-t-di'l'etflc material which is itself in honta'ct with the mercury forming the cathode pool. Such a modification is illustrated in Figs. 4 and 5, wherein parts corresponding to those 'aforede'serlbed have been given like numerals of-reterenee. ThHsJln-Figs. 4 and 5,'-we haveshown the hood '20 as provided 'withanrap' proximately pear-shaped opening z 0; :and formed integrally with or "fused "to the narrower upper endedge thereofiis "a glass'nib 20 which projects outwardly and then downwardly in suohialmanner that the lower end 20 penetrates, .oriis:lo est-ted belomi'the surface :of the cathode :pool 11. The exact r'eason for the "resultant phenomenon is -not -known, but it is believed thatv-the lower (nul -2U e1 'nib 20 aots'to 'oolleet andrstore the electrical charge's nf the 'ionlmed vapor particles, whieh discharge to the cathode in :such a manner -a's to prodiice almost instantanebus lyam are between thei'same'an'd the:surface of the mercury pool; th'e required potentialifor actual preclustion oi an are betweenrsuchrelementsbeing generated very rapidly. In Fig. 5 the dotted line H lridicates thenormal level ofthe cathode pool with respe'et to the end #2 0 :of the dielectric v nib in mg. 3 we have :shown a further modification; which is iunetl'onally :similavto that: shown mil i 'gsflt amt-'5. :HoWevenin-Figifi theaglass'hoed 20 i providerli-withia nireular :opening :20 whieh.

is r preferably ef substantially greater *area than the aforementioned :epenin'g 20. :Mter formatlonmf the'openln'gaz 0 111 any suitable manner a pair "of giass ro'ds fl about gomvmm in diameter, are laid fpa'raliel relationship lto each nther, with a space ot'eloeut i020 inch therebetween, l'I'heiopposlteends of rods "are thnms'ed-into the-maln'1bm1yofrh'ooid 20 in 'e relationship' toi provideftor *vertiealfpositloninz o'r sm roes whemube N iszin its operative potential 6f ljet [1 is' poleil right-with position, as indicated in Fig. 6, 'I-he arrangement is such that the aforementioned jet l'l is. directed, toward the surface of'the cathode pool through the slit between rods 28,,whereby contact of the jet with one or both of said rods is insured. The normal level of the cathode pool is indicated by the dotted line Fl in Fig. 6. j I

In the modified form of our invention shown'in Fig.-7 most of the parts illustrated may be identical with those shown in Fig. 1, and the same have been given corresponding numerals of reference. However, in Fig: 7 we employ-a-glass ring or annulus 29 having a notch 29 formed in the upper edge thereof as shown through which the vapor jet (not shown). may be ejected from opening 2|, into contact with the surface of the cathode pooll1. Thus'in Fig. 7 the dome-shaped upper end of the hood 20 of Fig. 1 has been omitted. The bell 2| of the boiler may be attached to ring 29. for support by the latter at, say, threeequally spaced points, by positioning and fusing a small quantity or bead of glass at each point, thus. forming rigid .connections between ring 29- and. bell 2| one of such connections being shown at 30. By eliminating the dome-shaped upper end of the hood (of Fig. 1) we minimize the possibility of collection or aggregation of the jet particles upon a dielectric surface in electrically insulated relationship to the cathode pool l1. we have found by experiment that the arrangement justdescribedimproves operating characteristics of the tube. It is to be understood, of course, thatwith a device like that of Fig. 7, suitable dielectrioelements like thoseillustratedat 20 20 in Fig. 4, or at 28 in Fig. 6, may, and preferably are, provided tO'CfiCt the ad'ditionaiimproved results aforedescribed. e

We-claim: v 1

.1. In a gridless power tube .havingtherein an anode and a mercurypool type cathode, a longlifed make alive starter requiring less than one watt of energy on sixty cycle power, said starter including a reconstructible body of mercury nor.- mally electrically separated from vtheniercuiy ofsaid cathode, said tube being operable withcuta holdingarc. I v i 2. In a gridless power tube havingtherein an anode and a mercurypool type cathode, a longlifed make alive starter requiring less than one watt of energy on sixty. cycle power, said starter. including a reconstructible 'mercury vapor jet electrode, the source of mercury ofsaid vapor jet comprising a reconstructible body of liquid mercury normally'electrically separated from the mercury of said cathode, said vapor jet elect-rode providing for operation of said tube withouta holding arc. s

3. In a gridless power tube having therein an anode and a mercury'pooltype cathodea longlifed make alive starter requiring less than one watt of energy on sixty cycle power, said starter including a continuously operable mercury vapor jet, the source of mercury of said vapor jet comprisinga reconstructible body of liquid mercury normally electrically separated from'the mercury of said cathode, andran auxiliary electrode in contact with said last mentionedbody: of merjcury to provide-for ionization ,of saidvapor jet, said vapor jet when-ionizedproviding for opera: tion of said tube without a holding arc. l

4. In a'gridless; power'tubehaving therein an anode and a mercury pool type cathode, a long lifed make alive starter requiring less than one Watt of energy on' sixty cycle power, said starter including a continuously operable mercury vapor jet, the source of mercury of said vapor jet comprising areconstructible body of liquid mercury normally electrically separated from the mercury of saidcathode, an auxiliary electrode in contact with said last mentioned body of mercury to provide for ionization of said vapor jet, said vapor jet when ionized providing for operation of said tube without a holding arc, and a refractory dielectric element itself in contact with the mercury of said cathode pool and located in the path of at least a portion of said vapor jet where the latter impinges on said cathode pool.

5. A power tube having therein an anode and a mercury pool type cathode, and means'comprising a; body of mercury normally electrically separated from the cathode for providing an ionized vapor jet starter for said tube. 6. A power tube having therein an anode and a mercury pool type cathode, means providing an ionized mercury vapor jet starter for said tube, said last mentioned means comprising a body of mercuryelectrically and mechanically separated from said cathode, heating means associated with said last mentioned body of mercury to vaporize continuously a portion of the same, and means including an auxiliary electrode for effecting ionization of said vapor jet.

7. A power tube having therein an anode and a pool type cathode, means providing an ionized vapor jet starter for said tube, said last men,- tioned means comprising a body of cathode material electrically and mechanically separated from said cathode, heating means associated with said body of cathode material to vaporize continuously a portion of the same, and means comprising an auxiliary electrode covered by the surface of said body .of cathode material to insure ionization of the vaporized portion thereof at will.

8.; A power tube having therein an anode and a pool type cathode, means providing an ionized vapor jet starter for said tube, said last mentioned means comprising a body of cathode material electrically and mechanically separated from said cathode, heating means associated withsaid body o'fcathode material to vaporize continuously a portion of the same, means comprising an auxiliary electrode covered by the surface of said body. of cathode material to insure ionization of the vaporized portion'thereof at will, and associated means for directing the ionized vapor in the form. of a jet against the surface of said cathode to effect production of a cathode spot upon the latter. 9. In a power tube, in combination, a sealed envelope having therein an anode and a reconstructible cathode, said envelope also having therein a chamber containing a body of the material of said cathode in insulated relationship to the latter, means for heating said body of material to effect vaporization of a portion thereof continuously, means for directing the vapor so generated under relatively high pressure against the surface of said cathode, and means including an auxiliary electrode electrically connected under the surface of said body of material to provide for ionization of said vapor at will.

i 10. In a power tube, in combination, a sealed envelope having therein an anode and a reconstructible cathode, said envelope also having therein achamber containing a body of the mate rialof said cathod in insulated relationship-to the latter, means for heating said body of material to effect vaporization of a portion thereof continuously, said chamber having a closed upper enemas end said chamber having an opening formed in a sidewall thereof tqprovid'e for overflowthereinto of the excess-of cathode. material, said opening also providing for passage of the vaporso. generated 'in the form of ajet from. said chamber against the surface of said cathode, and means comprising an auxiliary electrode electrically connectedfwith said bodyof material'beneath the surface of the. latter to provide forionization of said vapor at will.

11. In a power tube, in combination, a sealed envelope having therein an anode and a reconstructible cathode, said envelope ,also," having therein a chamber containing a body of "the material of saidicathode in insulated relationship. to the latter, means for rial to, effectvaporization of a portion'thereof continuously, said chamber having a closed upper end, said chamber having an opening formed in a side wall thereofto provide for overflow thereintoof the excess of cathode material, said opening also providing for passage of the vapor so generated in the form of a jet fromsaid chamberagainst thersurface of said cathode, means comprising an-auxiliary; electrode electrically connected with said body of material' beneath the surface of the latter to provide for ionization of said vapor at will, and means comprising a dielectric element in contact with the cathode surface, saiddielectric element being so positioned; as to insure contact of at .least a portion of said vapor jet therewith, at or closely adjacent the point of impingement of said jet against said cathode surface, atleast a portion of said dielectric element being in contact with said cathode.

12. In a; power tube having therein an'anode and a pool type cathode, the combination with means for continuously =reconstructing said cathode, saidmeansccmprising a well sealed to and depending from said tube, a body of cathode material positioned within said well in electrically insulated relationship to the cathode, means providing for overflow of the excess material from said cathode to said well, means for heating the material in said well to effect continuous vaporization of a portion of the same, means for directing the vapor so formed in a relatively small stream against the surface cathode, and means comprising an auxiliary electrode for effecting ionization of said vapor at will to facilitate formation of a cathode spot at or adjacent the point of impact of said vapor stream against said cathode surface.

13. In a power tube having therein an anode and a pool type cathode, the combination with means for continuously reconstructing said cathode, said means comprising a well sealed to and depending from said tube, a body of cathode material positioned within said well in electrlcally insulated relationship to the cathode, means providing for overflow of the excess material from said cathode to said well, means for heating the material in said well to effect continuously vaporization of a portion of the same, means for directing the vapor so formed in a relatively small stream against the surface of said cathode, and means comprising an auxiliary electrode in contact with the material in said well, said electrode cooperating with said cathode through said vapor to effect ionization of the latter at will to provide for substantially instantaneous formation of a cathode spot upon said cathode.

14. A power tube having therein an anode and heating said body of mateof said a pool type cathode, means providing an ionized vapor jet starter for said tube, said last mentioned means comprising a body of cathode material electrically and mechanically separated from said cathode, heating means associated with said body of cathode, material to vaporize continuously a portion of the same, means comprising an auxiliary electrode covered by the surface of said body of cathode material to insure ionization of th vaporized portion thereof at will, associated means for directing the ionized vapor in the form of a jet against. the. surface of said cathode to effect production of a cathode spot upon the latter, and means comprising a dielectric element in contact with said cathode and located in the path of at least a portion of said jet at or closely adjacent the point of impingement of the latter against said cathode surface.

15 In a power tube, in combination, a sealed container having therein an anode and a mercury cathode, said container also having sealed thereto and communicating therewith a chamber containing a body of mercury normally mechanically and electrically separated from said cathode, means for heating said separated body of mercury to effect vaporization of a portion thereof continuously, means for directing the vapor so generated in the form of a jet against the surface of said cathode, and an auxiliary electrode in contact with said separated body of mercury beneath the surface thereof, whereby said vapor may be ionized at will.

16. In a power tube, in combination, a sealed container having therein an anode and a mercury cathode, said container also having sealed thereto and communicating therewith a chamber containing a body of mercury normally mes chanlcally and electrically separated from said a hode aid cham er hav a closed upper end and an opening in a side wall thereof to afford the communication aforementioned, the lower portion of said opening forming a weir to provide for overflow of the excess quantity of mercury from said cathode to said chamber, means for heating said separated body of meru y to f e vapo ization of a po n th ccntinuously, the vapor so generated being adapted to pass in the form of a jet through the upper portion of said opening against the surface of said cathode, and an auxiliar electrode in contact with said separated body of mercury below the surface thereof, whereby said vapor may be ionized at will.

17. In a power tube having a reconstructible cathode, in combination, a chamber in said tube containing a body of the material of said cathode in normally insulated relationship to the latter, means for continuously heating said body of material to effect generation of vapor, means for directing the generated vapor in the form of a jet against the surface of said cathode, and electrical means associated with said body of material and operable under given conditions to effect ionization of said vapor, whereby initiation of conduction between said cathode and an associated anode is facilitated.

18. In a power tube, in combination, a sealed flask having therein an anode and a mercury pool cathode, said flask having a chamber sealed thereto and depending therefrom, a body of mercury partially filling said chamber and normally mechanically and electrically separated from said cathode, means providing for overflow of the excess of mercur from said cathode to said chamber, means for continuously applying a predetermined degree of heat to the mercury in said chamber to effect generation of vapor at a predetermined rate, means for directing the, vapor so generated in the form of a jet against the surface of said cathode, and an auxiliary electrode in contact with the body of mercury in said chamber and adapted upon energization thereof jointly with said anode and cathode to eifect ionization of said vapor, whereby formation of a cathode spot is facilitated.

19. In a power tube having an anode and a mercury pool type cathode, in combination, a chamber sealed to and depending from the lower end of said tube, a body of mercury partially filling said chamber and normally electrically insulated from said cathode, means providing for overflow of the excess mercury from said cathode to said chamber, a boiler located within said chamber, said boiler including a bell-shaped member the lower end of which is immersed in said body of mercury, a heating element positioned within said member and adapted to effect generation of mercury vapor continuously, said member having an opening formed therein through which said vapor is permitted to escape in the form of a jet, the arrangement being such that said jet is adapted to impinge against the surface of said cathode, and an auxiliary electrode electrically connected with said body of mercury to provide for ionization of said vapor jet at will.

20. In a power tube having an anode and a mercury pool type cathode, in combination, a chamber sealed to and depending from the lower end of said tube, a bod of mercury partially filling said chamber and normally electrically insulated from said cathode, means providing for overflow of the excess mercury from said cathode to said chamber, said chamber having a reentrant recess formed therein and projecting above the surface of said mercury body, a bell-shaped member surrounding said recess and having its lower end submerged within said body of mercury, whereby a relatively small portion of the latter is accommodated within said bell-shaped member, an electric heating element positioned within said recess and adapted to effect vaporization of the mercury of said body continuously, said bell-shaped member having an opening formed in a side wall thereof to permit escape of the generated vapor and to direct the same in the form of a jet against the surface of said cathode, and means including an auxiliary electrode located within said chamber to effect ionization of said vapor at will. I

21. In a power tube having an anode and a mercury pool type cathode, in combination, a chamber sealed to and depending from the lower end of said tube, said chamber having a reentrant recess formed therein, an electric heating element positioned within said recess, a tubular insulating member extending downwardly in spaced relation to the wall of said recess throughout the major portion'ot the length of the latter, whereby a relatively small portion of said mercury body has free access to the space between said insulating member and the wall of said recess, said insulating member having a wall portion thereof reflexed upwardly upon and in spaced relation to itself from itslower end throughout the major portion of its length to minimize the transmission of heat to the main portion of said mercury body, said reflexed wall portion having a multiplicity 'of outwardly projecting bosses formed integrally therewith to substantially center and stabilize said insulating member within said chamber, said insulating member having a downwardly angled opening formed in a side wall thereof, said heating element when energized being adapted to effect vaporization of the mercury of said body continuously, the resulting vapor being directed by said opening in the form of a jet against a given spot in the cathode surface, and an electrode immersed within said body of mercury and adapted when energized under given conditions to effect ionization of the vapor of, said jet, whereby starting of said tube is facilitated.

IRVIN W. COX.

LESTER D. DRUGMAND.

REFERENCES CITED The following references are of record in the file of this patent: I 

